1. Field of the Invention
The present invention relates to a component for a ball screw, and more particularly to a circulating member for a ball screw, which can eliminate the conjunction level difference and prevent the balls from being struck.
2. Description of the Prior Art
Nowadays, ball screw is used more and more widely in modern industries. As a linear transmission means, the ball screw not only has high precision but also has the advantages of low frictional loss, high energy conversion ratio, low noise and high rigidity. Hence, it is self-evident that the ball screw is very important to various industrial mechanisms.
In order for the balls between the screw and the nut to circulate smoothly and for eliminating the circulating impact force caused therebetween, the nut is usually provided at both ends thereof with a circulating member (for example, circulating cap). And the circulating member is a key member for enabling the balls circulation from the screw and the nut. Therefore, how to develop an improved and competitive circulating cap is the common goal that the manufactures are striving for.
The conventional circulating members are shown in FIGS. 1, 2 and 3.
FIGS. 2 and 3 show an ordinary conventional circulating structure, and FIG. 1 shows a circulating member disclosed in U.S. Pat. No. 2,618,166, wherein the conventional ball screw comprises: a nut 10, a screw 11, a plurality of balls 12, and a circulating member 13 installed radially from outside into inside of the ball screw. The circulating member 13 is inserted in the nut 10 via the hole 101 and serves to cooperate with the Gothic type (Gothic type or Gothic shape is a pointed arch) thread 102 to guide the balls 12. The balls 12 climb over the ridge of the threads of the screw 11 and move from one thread 102 to the other neighboring thread 102 through the return path 131 of the circulating member 13 connected between two neighboring threads 102. The two neighboring inner threads 102 of the nut 10 are connected with the return path 131 of the circulating member 13 to form an enclosed circulating path for enabling the balls to circulate endlessly. The structures shown in FIGS. 2 and 3 are the same in design, therefore, they are designated with the same reference numbers. These conventional circulating structures have the disadvantages as follows:
When the balls 12 move into the return path 131 of the circulating member 13, since the inner threads 102 of the nut 10 are of Gothic type, but the return path 131 of the circulating member 13 is a circular arc-shaped passage. Inevitably, at the conjunction between the return path 131 of the circulating member 13 and the inner threads 102 of the nut 10 appears a non-continuous level difference X and consequently the balls 12 are likely to be struck or jammed by the level difference X when moving in and out of the circulating member 13, and consequently, the balls 12 can't move smoothly.
The aforementioned circulating member 13 generally refers to a cap piece, an engaging piece, or the like, used to connect the thread for enabling the balls to circulate. The circulating path 131 is circular arc-shaped and constant in cross section. Since the circulating path 131 can't flushly abut the inner threads 102 of the nut 10, inevitably, there will exist a level difference X, and consequently, the balls will strike the level difference X.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.